docs: def remove_perm(perm, user_or_group, forum=None):
      """ Remove a permission to a user (anonymous or not) or a group. """
      user, group = get_identity(user_or_group)
      perm = ForumPermission.objects.get(codename=perm)
      if user:
          UserForumPermission.objects.filter(
              forum=forum,
              permission=perm,
              user=user if not user.is_anonymous else None,
              anonymous_user=user.is_anonymous,
          ).delete()
      if group:
          GroupForumPermission.objects.filter(forum=forum, permission=perm, group=group).delete()